Textile machine

ABSTRACT

An electrostatic spinning apparatus in which the electrostatic field through which textile fibers are caused to flow is enhanced, and has a stabilized configuration by minimizing the transient charge accumulation in the area adapted to receive the fibers and by mitigating air turbulence so as not to disrupt the desired flow path of the fibers.

[451 May 30, 1972 d Floyd ABSTRACT United States Patent Amato [54] TEXTILE MACHINE XX 96 0&5 8H 7 75 5m Wm .z me m wm .n a hm C 13 76 99 l1 UW 1 200 17 14 27 50 5l.. 33 n, ,m o, t m A d r 8 .h .m R E O t n e V n l l 2 7 I [73] Assignee: Electrospin Corporation, Columbus, Ohio Pfima'y Examiner-Werner H- Schroeder [22] Filed: Allg. 25, 1970 [21] ApplfNo.:4 66,716

Attorney-John R. Bronaugh, E. Dennis OConnor an S. Levison Patented May 30, 1972 0 t u m A. WM Vf N0 Inh .w R

`TEXTILE MACHINE BACKGROUND OF THE DISCLOSURE The invention relates to improvements in electrostatic spinning apparatus that enhance the eective strength and control the configuration of the electrostatic field through which textile fibers flow immediately prior to their being received by the means for twisting and spinning them into a continuous strand or yarn.

ln known electrostatic spinning devices, such as that shown in U.S. Pat. No. 3,41 1,284, issued Nov. 19, 1968 to A. Corbaz et al. for Method and Apparatus for Spinning Textile Fibers," the electrostatic field extends across an air gap between a drafting system that mechanically advances the fibers into the field and a spinning head for twisting and spinning the fibers to form yarn. The fibers are supplied to the drafting system in the form of roving or sliver and are discharged from the drafting system asa stream of discrete fibers into the electrostatic field. The field is effective to align the fibers and define a flow path which the fibers follow to the spinning head.

Reliability of spinning fibers by the electrostatic spinning process is dependent upon the strength and stability of the electrostatic field, and upon minimization of air turbulence created by the-twisting device in the area of its fiber-receiving end.

lri the present invention, the field between the receiving electrode and ground is reinforced in the fiber transport zone by partly filling the field with a dielectric material surrounding the receiving electrode. When the dielectric material conforms to an equipotential surface, there are no voltage gradients along the dielectric surface and, therefore, no tendency to build up charge accumulations. These accumulations tend to distort the field and become transient in nature by appearing and disappearing as surface resistivity changes because of humidity or contamination. Air turbulence in the area of the fiber-receiving end of the twisting member increases fiber waste by deflecting the fibers from their intended path of travel.

The dielectric material located and formed according to the present invention increases substantially the reliability of electrostatic spinning of textile fibers by providing a means which reinforces the electrostatic field and shapes it to facilitate focusing of the fibers toward the receiving end of the twisting member as well as stabilizing the field configuration by minimizing transient charge accumulations in-the area adjacent to the receiving end. Additionally, this body of dielectric material further enhances the reliability of this form of spinning by mitigating to a large extent the air turbulence in the area surrounding the `fiber-receiving end of the twisting member.

SUMMARY OF THE INVENTION The fiber-receiving end of the spinning head is made of a dielectric material and is disposed so as to protrude from an annular, substantially hemispherical, highvoltage electrode which provides a converging electrostatic field and maximum field focusing and strength. The yarn gripper is rotatably carried within a support and the dielectric cap is fixed to the upper end of this support. The cap includes a centrally disposed through opening within which the gripper is rotated and the filling receiving end thereof is disposed so that its surfaces extend substantially continuous with the exposed dielectric surface of the cap. By providing only sufficient clearance for the fiber-receiving end of the gripper spindle to rotate within the through opening of the cap, the air turbulence in this area is minimized.

The configuration of the cap is also hemispherical and being made of a dielectric material strengthens the eld in the fiber transport zone while maintaining the direction of the field vectors. By shaping the dielectric surfaces of the cap to correspond to the equipotential surfaces of the field, there is no resultant change in the direction of the electric eld vectors. This increased eld strength provides improved fiber control at no increase in overall voltage. The cap configuration also permits the field lines to pass through its dielectric surface normally which maintains a stable field configuration, thereby reducing substantially the possibility of defocusing these lines and creating charge accumulations that vwould be transient in nature.

It is a general object of the present invention to provide an improved electrostatic spinning apparatus having a strong, stable field configuration within which textile fibers are aligned and transported to the means for twisting and spinning them into continuous strand material.

A more specific object ofthe invention is to provide an electrostatic spinning apparatus which, in addition to having a strong and stable field, has improved fiber control, substantially reduced transient charge accumulation due to potential gradients along its surface and minimal turbulence in the area of the fiber-receiving end ofthe twisting member.

These and other objects of the present invention will become more fully apparent by reference to the appended claims and as the following detailed description proceeds in reference to the single figure.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a partially schematic longitudinal section of a portion of an electrostatic spinning apparatus according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The spinning apparatus shown embodies avdrafting system l0. This drafting system 10 is quite similar to that described with reference to FIG. 4 in the article entitled The Development of Electrostatic Spinning" by V. P. Radovitskii et al, Tekst. Prom. (Moscow) 29 No. 10, 36-41 (1969) and comprises a pair of power driven inlet drafting rolls A11 and ll2 between-which roving or sliver is fed. A pair of power driven intermediate drafting belts 13 and 14 entrained respectively about drive rolls 15 and 16 and nose bars 17 and 18 and an idler roll 18a which guide and position the belts 13 and 14 so as to direct the fibers being advanced therebetween to a pair of fiber discharge drafting rolls 19 and 20. The draft of the drafting system 10 is sufficiently high that the discharge from rolls 19 and 20 is a stream of discrete fibers. Drafting roll 19 is of a conductive material, such as metal, and is grounded as indicated. Drafting roll 20 comprisesa central conductive core 20a which is grounded and a dielectric sleeve 20b in rolling contact with roll 19 as shown. Below and spaced from the discharge rolls 19 and 20 is the spinning head assembly 21. Assembly 2l includes a normally stationary body 22 and end caps 23 and 23a mounted respectively on the upper and lower ends of body 22.

A spindle 24 is joumaled in body 22 by axially spaced aligned anti-friction bearings 25 and 26 fixed within the central through bore 27 of the body 22. Body 22 has a laterally extending side opening 28 to the enlarged central portion 29 of the spindle 24 which is frictionally driven by an endless belt 30 extending through opening 28 and continuously rotated by a drive portion of the spinning apparatus (not shown).

Spindle 24 has an axial through bore 31, the lower end of which denes `a yarn discharge opening 32 from which spun yam (not shown) is drawn by take-up or drawing rolls 33 and 34.

The upper end of the spindle 24 is counterbored at` 35 to receive a gripper 36 into which fibers (not shown) are directed to be twisted and spun into yarn. Gripper 36 may, for example, be of one of the types illustrated in U.S. Pat. No. 3,372,537, issued Mar. 12, 1968 to M. Poull et a1. for Radially Clamping Grips.

The upper end of the spindle 24 has an extension 37 defining a conical fiber inlet opening. This extension is made of a trally disposed through opening 38 in the cap 23.

The fiber-receiving end of extension 37 has a funnel-shaped aperture 39 terminating in a cylindrical opening 39a in axial alignment with and substantially equal in diameter to the inlet end of the gripper 36. The adjacent end of gripper 36 is normally conductive while the extension 37 is of dielectric material. A yarn tail extends through opening 39a from gripper 36 into the aperture 39 and fibers from rolls 19 arid 20 are captured and presented to the yarn as the tail rotates through the maximum field where the tail is maintained. The top peripheral edge of the funneled aperture 39 is in close proximity to the wall of the through opening 38 provided in the cap 23, which is also of dielectric material, so as to provide a minimum amount of clearance between these two elements. With this closeness of assembly, the surface of the funneled opening 39 extends substantially continuous with the outer exposed surface of the cap and the possibility of air turbulence created by rotation of the spindle 24 is substantially eliminated.

The annular metallic negative electrode, or cathode, 40 of the electrostatic system is fixed within the body 22 of the spinning head 21 in axially aligned surrounding relation to the spindle 24 below the cap 23. This electrode 40 is connected by a lead 41 to a terminal of a high voltage electrostatic power supply, the other terminal of which is grounded. The upper external surface of electrode 40 is a segment of a sphere for maximum field focusing and strength. The metallic upper end of the gripper 36 in effect forms a continuation or extension of electrode 40, thus effectively providing a substantially hemispherical cathode.

The configuration of the electrostatic field is represented by dotted lines 42 as it extends from the outer dielectric surface of the cap 23 to the metallic portions of the rolls 19 and 20 that provide the ground for the electrostatic field. Cap 23 is annular, coaxial with spindle 24 and has an external surface which is a segment of a sphere substantially concentric with the center of the spherical surface of the electrode 40 so that its exposed dielectric surface is approximately nomia] to the field lines.

As disclosed in the aforesaid Corbaz et al. patent, the electrostatic spinning process uses a high voltage electric field to focus fibers into a rotating funnel. The surrounding negative electrode, or cathode, within which the funnel is coaxially journaled preferably approximates a small hemisphere as disclosed herein for maximum field focusing and strength. The funnel (spindle extension 37) is made of a dielectric material and necessarily protrudes axially from the cathode 40. As disclosed herein, it is surrounded by a dielectric cap 23 to reduce disruptive air turbulence. An improperly designed cap, such as a cup configuration, would tend to defocus the field in the spinning zone. The cap 23 is designed so that, in addition to reducing the air turbulence, it assists in providing the proper field shape.

By designing the cap 23 with dielectric surface corresponding to equipotential surfaces, there is no resultant change in the direction of the electric field vectors.

As shown in the drawing, the equipotential surfaces 43 at various radial distances from the hemisphere corresponding to the top of the funnel inlet of the spindle extension 37 are approximately concentric spheres. The hemispheric cap 23 is designed as a reasonable compromise between the exact shape necessary to correspond to an equipotential surface and a shape which would be easy to manufacture. Design of the cap 23 in this form has two additional advantages. The second advantage is that the field strength in the air gap between the rolls 19 and 20 and the cathode 40 is increased. If the surface of the dielectric corresponds exactly to an equipotential surface, the field strength is increased by the factor:

where v" is 'the value of the equipotential surface before the dielectric is added, and v is th e total potential difference between electrodes, and e is the dielectric constant. Most solid The third benefit results from the fact that the field lines 42 pass through the dielectric surface normally. Should the feldv lines emerge at some angle different from There would be a component field strength tangential to the dielectric surface. Because of the finite conductivity of this surface, this would result in a current which, in turn, would create charge accumulations at certain locations on the cap. These accumulations would produce additional distortion of the field. They would be transient in nature, appearing and disappearing as surface resistivity changed because of humidity or contamination. The cap 23 eliminates this problem. Such transient localized charge accumulations will not occur, and hence the field configuration will remain stable.

To summarize the operation, the textile fibers are fed into the drafting system in the form of roving or sliver. The fibers leave the rolls 19 and 20 as a stream of discrete fibers and immediately enter the electrostatic field, which is effective to align and transport them to the fiber-receiving end of the spindle 24. The dielectric cap 23 according to the invention has a configuration which corresponds to the equipotential lines of the electrostatic eld and is effective, in addition to providing the desired field shape, to strengthen and stabilize the field, thereby providing substantially improved control of the fibers. The fibers after entering the receiving end of the twisting member are received by the gripper 36 that is effective to twist and spin them into yarn.

The yarn is drawn from the spindle 24 through its discharge opening 32 by means of the rolls 33 and 34 and is wound upon any suitable spool or the like not shown.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

I claim:

1. Ari open end spinning apparatus for textile fibers having a fiber advancing device and a fiber twisting device rotatably carried in a support housing spaced from said advancing device by a gap, said twisting device having a fiber inlet end and a yarn discharge end with means intermediate said ends for twisting and spinning said fibers into yarn, means establishing an electrostatic field across said gap between said advancing device and twisting device for transporting said fibers from said advancing device to the receiving end of said twisting device, and a body of dielectric material interposed between said advancing device and said twisting device within said electrostatic field, said body of dielectric material having a configuration substantially conforming to the equipotential surfaces of said electrostatic field.

2. The apparatus defined in claim l wherein said fieldestablishing means includes an annular electrode surrounding said twisting device and wherein the dielectric body is annular and coaxial with said annular electrode and the exposed surface of said dielectric body opposed to said fiber advancing device across said gap has a configuration substantially conforming to the equipotential surfaces of said electrostatic field from said annular electrode, thereby precluding resultant change in the direction of the electric field vectors at the surface of said annular body.

3. The apparatus defined in claim 2 wherein said electrode and dielectric body have substantially concentric surfaces in the form of segments of spheres opposed to said fiber advancing device across said gap.

4. The apparatus defined in claim l wherein the dielectric constant of said dielectric material is in the order of 3 to 4.

Dedication 3,665,695-[22'07LW6Z A. Amato, Bolton, Mass. TEXTILE MACHINE. Patent dat-ed May 30, 1972. Dedication led Mai'. 23, 1977, by the assignee, Eleozhospz'n Oorpomtz'on. Hereby dedicates to the Public the entire term of said patent.

[Oficial Gazezfte May 10, 1977.] 

1. An open end spinning apparatus for textile fibers having a fiber advancing device and a fiber twisting device rotatably carried in a support housing spaced from said advancing device by a gap, said twisting device having a fiber inlet end and a yarn discharge end with means intermediate said ends for twisting and spinning said fibers into yarn, means establishing an electrostatic field across said gap between said advancing device and twisting device for transporting said fibers from said advancing device to the receiving end of said twisting device, and a body of dielectric material interposed between said advancing device and said twisting device within said electrostatic field, said body of diElectric material having a configuration substantially conforming to the equipotential surfaces of said electrostatic field.
 2. The apparatus defined in claim 1 wherein said field-establishing means includes an annular electrode surrounding said twisting device and wherein the dielectric body is annular and coaxial with said annular electrode and the exposed surface of said dielectric body opposed to said fiber advancing device across said gap has a configuration substantially conforming to the equipotential surfaces of said electrostatic field from said annular electrode, thereby precluding resultant change in the direction of the electric field vectors at the surface of said annular body.
 3. The apparatus defined in claim 2 wherein said electrode and dielectric body have substantially concentric surfaces in the form of segments of spheres opposed to said fiber advancing device across said gap.
 4. The apparatus defined in claim 1 wherein the dielectric constant of said dielectric material is in the order of 3 to
 4. 